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I found some burn marks on the plug-in of my microwave. The wall outlet was also burned. I replaced the oven and had an electrician wired in a new 110v recepatcle. Now the same things happened again. Any idea where to start looking. I left the new microwave unplugged. No problems with the other appliances on the circut.
How old is your house? I remember some years ago reading about an "experiment" with aluminum wiring that was later found to be starting fires in the manner that you mentioned-- it was noticed when burn marks were seen at the outlets.
I'm surprised that the electrician's visit didn't solve the problem. Perhaps a whole-house inspection by a different licensed electrician could help. Find out if that particular path on the wiring is solely for that outlet or is maybe split off and is handling more than allowed??
Edit: Sorry, read your post again. It would be wise to find out if that circuit is handling the proper load.
A common problem with receptacles is loose wiring on the connection points of the terminals of the receptacle. A loose wire will also make for a bad connection and cause an unusual amount of heat buildup. Loose connections can also cause sparking in the junction box that can result in arcing. You'll likely see burn marks around the terminals if this happens. This is a likely electrical fire in the works if not corrected immediately.
Do you have fuzes or circuit breakers?
Do you know the wattage of your microwave? Probably 1000, 1200, or 1500 watts
Do you know how many outlets are on the circuit? What else is plugged into the outlets?
Do you know if it is a 15 Amp circuit or a 20 Amp circuit.
Ideally your kitchen should have 20 Amp circuits (which is a thicker wire than 15 Amp circuits). If possible a microwave should have it's own circuit.
Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
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A microwave should have it's own circuit, though most of the less powerful ones are usually OK without. This sounds like you are close to blowing the circuit breaker with an overload, not enough amps in that circuit. Find out what the label says on the breaker. If it's an old house with fuses, there were no microwaves then and you may not have large enough wiring to handle it. Too bad you already bought a new one, I would have suggested a lower wattage unit. Bigger ones may be 1,200 watts, while some smaller ones are only 600. That makes a big difference to the wiring.
Is the back box metal? Something could be touching. If its a older house then you may be overloading the circuit. Some older houses did not have one specific circuit per appliance.
How old is your house? I remember some years ago reading about an "experiment" with aluminum wiring that was later found to be starting fires in the manner that you mentioned-- it was noticed when burn marks were seen at the outlets.
Update: I pulled the wall receptacle and the copper wire was in tight. The circuit is confined to a dining room with nothing else on but a light fixture with three 60watt bulbs. I'm waiting for MR. Sparky, the electrician, to show, but I'm betting the high-wattage is just too much for the circuit.
Something does not add up here??? Is your electrician a licensed electrician or is he a "handyman" type?
Or is this a rental and the "electrician" is being provided by the landlord?
Basically if everything is wired properly, the above problem should not happen. That includes a properly sized circuit breaker / wire and the microwave plug is in good condition (not melted) - outlet in good condition. Proper voltage on circuit as measured with a voltmeter with microwave running.
If this continues to be a problem and it is your house, get another electrician who is licensed. Then have him install a new dedicated 20 amp circuit / outlet for that microwave. Get a commercial grade (good quality) outlet. Replace cord on microwave if it was damaged.
Also replace the circuit breaker on the old circuit "just because". The breaker should trip if the circuit is overloaded. Note there are some breakers which do not trip when they should (Federal Pacific) and China has manufactured counterfeit breakers which may not work as they should. Google the circuit breaker brand and model numbers to see if there are any reported problems with them.
Last edited by Billy_J; 11-04-2013 at 09:32 AM..
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Loose wires
